Method of and means for producing harmonics



July 20,1 2 1,592,937

Y J. $.JAMMER METHOD OF AND MEANS FOR PRODUCING HARMONICS Filed Dec. 27. 1921 //'71 e/7/0/ Jami J Jammer Patented July 20, 1926. UNITED STATES PATENT OFFICE. noon s. anemia. or CUMBERLAND, MARYLAND, assrenoa r wns'rnnu ELECTRIC COMPANY, mconroaarnn, or NEW YORK, N. Y., A coaroaarron on NEW Yoax.

METHOD OF AND MEA NB FOR PRODUCING HARMONICS.

Application filed December 27, 1921. Serial No. 524,883.

the divided output circuit, the base frequency and the odd harmonics are accentuated; while in the work circuit connected to the common output circuit, the even harmonics are accentuated. The individual harmonics are then selected by means of tuned circuits.

A means for equalizing the amplitudes of the generated harmonics is also provided which comprises a common amplifier for amplifying the 'higher harmonics as a group This invention relates to a method of and means for producing harmonics of a base frequency.

One object of the invention is to provide a method of and means for combining ourrents derived from the output circuits of a plurality of distorted wave producing de- Vices in such a way that the harmonics are accentuated and a selective separation of the harmonics facilitated. Another object is the provision of a method of and means for combining such output currents in such a way that the base frequency and the odd harmonics are available in one work circuit and the even harmonics in another and separate work circuit.

It is well known that a base frequency alternating current wave may be distorted in a wave distorting device, such as a magnetic transformer or a thermionic vacuum tube, and that the base frequency and the harmonies may be selected from the output circuit of such a device by means of selective circuits. One way of doing this is shown in British Patent No. 142,571 of 1.920. In s stems of this kind, not only do the relative amplitudes of the harmonics decrease very rapidly as their position in the harmonic scale increases, but in practice there is a minimum limit to the spacing between the harmonics below which it is lmpractical to go, due to the increased cost of selective circuits. In one case it has been found that a base frequency of 5,000 cycles per second, giving a harmonic spacing of 5,000 cycles, is about the lower practical limit.

Under the same circumstances, b employing the principles of this invention, it is practically possible to derive harmonics from a base frequency as low as 2,500 cycles per second and to practically separate them from one another.

In one embodiment ofthe invention two three-electrode thermionic vacuum tubes are connected together by means of a divided input circuit and both a divided and a common output circuit. A common base frequency circuit is connected to the divided input circuit. There are two work circuits, one connected to the divided output circuit and the other to the common output circuit. In the work circuit connected to monies connected to the output of this amplifier.

In one aspect the two three-electrode tubes may be considered as devices which convert energy from a direct current source into alternating current of a base frequency and its harmonics. The base frequency is determined by the cyclic application of otential to the grids and the base frequencies from the two devices are 180 out of phase. Therefore any arrangement of circuits which gives the effect, which is obtained with three-electrode tubes, comes within the scope of this invention.

It is to be understood that the invention is not limited to its embodiment in a system as described just above, nor to the system to be described in detail hereinafter.

In the figure of the drawing, a harmonic generating system employing space discharge tubes in push-pull relation is illustrated.

The preferred embodiment of the invention will now be described in connection with the accompanying drawing. An oscillat-ion generator 0 of any suitable design supplies the base frequency current for the harmonic producer HP. The oscillation generator consists preferably of a threeelectrode vacuum tube 5 having an input circuit 6 and an output circuit 7. In order that some of the output current may be fed back to the input circuit to cause the generation of oscillations, a coupling transformer 8 is provided across one winding of which is connected a variable condenser 9. The ca pacity of this condenser together with the self-inductance of the transformer winding comprises a tuned circuit which determines the frequency of the generated oscillations.

and selective circuits for the higher har- I Energy for the plate circuit is su plied in the former was devised by monies in work circuit) 21.

usual way by battery 10 throng the choke coil 11. Resistances 12 and 13 are adapted to regulate the performance "of the oscillation generator. Transformer 14 is adapted to transfer the energy from the oscillation generator to the harmonic producer.

The harmonic producer comprises two three-electrode thermionic vacuum tubes 16 and 17, each having a cathode or filament, an anode or plate and an impedance controlling element or grid. The filaments are supplied with heating current from batteries and are conductively connected together. The plate circuit of each of the tubes 1s supplied with energy from the battery 18. T e grids are connected to opposite ends of the secondary winding of the transformer 14, while the filaments are connected to the midpoint of this winding. By this connection, alternating potential supplied by the osclllation generator 0 is impressed simultaneously upon the grid-filament circuits of each of the tubes 16 and 17, but in opposite hase.

In the output or filament-plate circuits two transformers 19 and 20 are arranged to transmit output current to two work circuits 21 and 22. The windings of transformer 19 are adapted to subtract the output voltages or to combine them differentially and so produce the base frequency and odd har- Transformer 20 adds the voltages in the output circuit or combines them additively and thus supplies the even harmonics to work circuit 22.

A circuit of this general type for use as a modulator but with only one output transolm R. Carson and is disclosed in British Patent No. 102,503 of 1917. The mathematical analysis contained therein shows that, by combining the output voltages a'dditively, the fundamental frequency and odd harmonics are suppressed and the even harmonics accentuated in the output circuit. 'By a similar process of reasoning it can be shown that, by combining the out ut voltages differentially, the even harmonics can be suppressed: while the base frequency and odd harmonics can be accentuated. It is also pointed out in Mr. Carsons analysis that, by proper design of the circuits, the output voltages corresponding to the fourth and higher power terms of the input voltage can be made negligibly small; so by a lfferent design they may be made relatively large and such a design would be used in racticing this invention, where it is desired to accentuate the barmonics.

Across the conductors of work circuit 21 are bridged a number of tuned circuits 23, 24, 25 and 26 tuned to the base fre uency and the-first, second and third 0d harmonies respectively; while across the conductors of work circuit 22 are bridged tuned circuits 27, 28, 29 and 30, tuned respectively to the first, second, third and fourth even harmonics. By means of coupling transformers, the energy of these circuits is impressed upon circuits n, 3, 5, '7", 2, 4, 6" and 8, respectively.

An amplifier A is provided to amplify as a group the higher odd harmonics such as the second, third and higher odd harmonies, the second and third being represented by circuits 5 and 7. This amplifier preferably consists of a three-electrode thermionic vacuum tube 34 having a grid, plate and filament. The higher harmonics as a group are impressed upon the rid circuit of amplifier A by means of transformer 35 and potentiometer 36. The operation of a tube for this purpose is well known and no further description will therefore be given.

Likewise an amplifier A which preferably consists of a thermionic vacuum tube 37 is employed to amplify the higher even harmonics as a group.

In order to prevent short circuiting the tuned circuits 23 and 24, the transformer 35 is so designed that it offers high impedance to the base frequency and first odd harmonic, to which frequencies circuits 23 and 24 are tuned respectively. In some cases it may be desirable to use a low impedance transformer 35 and to obtain the high impedance effect by means of a translating device, which offers hi h impedance to the base frequency and first odd harmonic, while offering low impedance to the higher harmonics. A wave filter, such as described in Campbell Patent No. 1,227,113 of May 22, 1917 could be used for this purpose by inserting it between the transformer 35 and tuned circuit 24. A filter having series capacity-elements and shunt inductance elements would be suitable for this purpose.

The same kind of translating device or filter could be used for the even harmonics by inserting it between the input transformer of amplifier A and the tuned circuit 28. In fact identical devices or filters could be used in both locations providing only that they be able to discriminate between frequencies differing from each other, by the value of the base frequency.

Each selected harmonic may in turn have its individual amplifying device such as amplifier A for amplifying the second odd armonic, and an amplifier A for amplifying the second even harmonic. For purposes of description, only two such amplifiers are shown. Obviously, others may be used wherever conditions so require.

The harmonic generator of this invention is especially adapted for use in avcarrier wave signaling system such as is described in British Patent No. 131,426 of November Ill! 13, 1919. The method of using it in such a system is obvious and, therefore will not be further described.

The scope of the invention is to be vlimited onl by the appended claims.

at is cla1med is:

1. A method of producing a plurality of differentfrequency periodic electromotive forces which comprises producing an electromotive force of a given base frequency, acting to cause said force to produce current in a plurality of channels, independently distorting the current in each channel and combining the waves resulting from distortion to give a group of waves of frequencies which are even multiples of said base frequency and another group which are odd multiples of said base frequency.

2. method of producing a plurality of different frequency alternating currents which comprises producing a base frequency current, distorting said current into a plurality of components of different frequen-.

cies, combining said components resulting rom distortion to give a group of components having frequencies which are e en multiples of said base frequency and another roup which are odd multiples of said base requency, dividing each group into smaller groups, increasing by amplification the energy of at least one of said smaller groups collectively, and selecting currents of individual frequencies from the amplified ener y.

3. A method of producing harmonic frequency waves which comprises producing a base frequency current, directing said current into a plurality of asymmetric channels, distorting'the current in each channel separately to fproduce a plurality of waves of different requencies, combining the waves resulting from distortion to give a group of waves of even harmonic frequencies of said base frequency, and to give another group of waves of odd harmonic frequencies of said base frequency, amplifying the higher harmonic waves of one group as a group, and selecting the individual higher harmonic frequency waves from said amplified group.

4. In a system of harmonic production, a source of electric current of base fre uency, a plurality of wave distorting devices, means to impress base frequency current differentially upon said distorting devices, two work circuits, output circuits individual to said devices, means to connect one work circuit differentially with said output circuits, and other means to additively connect the other work circuit with said output 1 circuits.

5. In a system-of harmonic production, a

source of base frequency alternating current, a plurality of thermionic vacuum tube wave distorting devices, means to impress base frequency current differentially upon said distorting devices, two work circuits, an output circuit for each of said devices, means to connect one work circuit differentially with said output circuits, and other means to connect the other work circuit cumulatively with said output circuits.

6. In a system of harmonic production, a source of base frequency alternating current, a plurality of thermionic vacuum tubes each having a grid, a plate and a filament, means to Impress base frequency current differentially upon the grids of said tubes, two work circuits, means to connect one work circuit differentially with respect to the plates of said tubes, and other means to connect the other work circuit additively to the plates of said tubes.

In a system of harmonic production, a source of base frequency alternating current, a plurality of thermionic vacuum tubes each having a grid, a plate and a filament, means to impress base frequency current differentially upon the grids of said tubes, two work circuits, means to connect one work circuit differentially with respect to the plates of said tubes, other means to connect the other work circuit additively to the plates of said tubes, selective circuits comprising variable condensers bridged across said work circuits to select currents of individual harmonics, and a common amplifier connected to one of said work circuits to amplify the higher harmonics as a group.

8. In a system of harmonic production two substantially identical devices each adapted to supply alternating current of a base frequency and some currents of harmonic frequencies, means to cause the base frequencies to be 180 out of phase, means to combine the frequencies from both devices additively and other means to combine them differentially.

9. In a system of harmonic production two substantially identical devices each capable of producing harmonics from a current of base frequency, a source of base frequency current, means to simultaneously supply base frequency currents 180 out 'of phase to said devices, means to combine'the generated harmonic currents from both devices additivel and other means to combine said currents tifferentially.

In witness whereof, I hereunto subscribe my name this 23rd day of December A. D.,

JACOB S. JAMMER. 

